Rotary actuator

ABSTRACT

An actuator system having a controlled element configured for rotary movement about a first axis relative to a reference structure; a linkage system between the element and reference structure; a first actuator and a second actuator configured to power a first degree of freedom and an independent second degree of freedom of the linkage system, respectively; the linkage system having a first link configured for rotary movement about a second axis not coincident to the first axis and second link configured for rotary movement about a third axis; the linkage system configured such that a first angle of rotation may be driven independently of a second angle of rotation between said first link and said reference structure; wherein one of the first or second actuators is configured and arranged to drive rotation of the element about the first axis when the other is operatively locked.

TECHNICAL FIELD

The present invention relates generally to the field of actuatorsystems, and more particularly to an electromechanical redundantactuator.

BACKGROUND ART

Redundant actuator systems are generally known. These systems typicallyarrange multiple actuators in a way in which their displacement issummed, or their torque is summed.

BRIEF SUMMARY OF THE INVENTION

With parenthetical reference to the corresponding parts, portions orsurfaces of the disclosed embodiment, merely for the purposes ofillustration and not by way of limitation, the present inventionprovides an actuator system (100, 200) comprising: a controlled element(180, 280) configured for rotary movement about a first axis (105, 203)relative to a reference structure (110, 210); a linkage system (170,270) connected to the element and the reference structure; a firstactuator (120, 220) configured and arranged to power a first degree offreedom of the linkage system (123 relative to 122, 223 relative to222); a second actuator (140, 240) configured and arranged to power asecond degree of freedom of the linkage system (143 relative to 142, 243relative to 242), the first degree of freedom and the second degree offreedom being independent degrees of freedom; the linkage system havinga first link (123, 223) configured for rotary movement about a secondaxis (104, 204) relative to the reference structure; the first axis andthe second axis not being coincident; the linkage system having a secondlink (143, 243) configured for rotary movement about a third axis (105,205) relative to the reference structure; the first link and the secondlink coupled (160, 260) such that rotation of the first link about thesecond axis in a first direction (126, 146, 226, 246) causes rotation ofthe second link about the third axis in a second direction (126, 146,226, 246); the linkage system configured and arranged such that a firstangle of rotation (144, 244) between the element and the referencestructure may be driven independently of a second angle of rotation(125, 225) between the first link and the reference structure; whereinone of the first or second actuators is configured and arranged to driverotation of the element about the first axis when the other of the firstor second actuator is operatively locked

The first axis (105, 203) and the second axis (104, 204) may besubstantially parallel and operatively offset a substantially constantdistance. The first axis (203), the second axis (204) and the third axis(205) may be substantially parallel and operatively offset asubstantially constant distance. The third axis may be substantiallycoincident with the second axis (104). The first link and the secondlink may be coupled with a coupling comprising a connecting link (160)having a first pivot (160 b) and a second pivot (160 c). The couplingmay comprise a bar link (160 a) between the first pivot and the secondpivot. The first link and the second link may be coupled with a couplingcomprising meshed gears. The first link and the second link may becoupled (160, 260) such that the first direction of rotation (126, 226)of the first link is opposite to the second direction of rotation (146,246) of the second link. The first link and the second link may becoupled (260′) such that the first direction of rotation (226′) of thefirst link is the same as the second direction of rotation (226′) of thesecond link. The actuator system may further comprise: a third actuator(320) configured and arranged to power a third degree of freedom of thelinkage system (323 relative to 322); a fourth actuator (340) configuredand arranged to power a fourth degree of freedom of the linkage system(343 relative to 342), the third degree of freedom and the fourth degreeof freedom being independent degrees of freedom; the linkage systemhaving a third link (323) configured for rotary movement about a fourthaxis (304) relative to the reference structure; the linkage systemhaving a fourth link (343) configured for rotary movement about a fifthaxis (305) relative to the reference structure; the fourth axis and thefifth axis not being coincident with each other or with the first axisor the second axis; the third link and the fourth link coupled (360)such that rotation of the third link about the fourth axis in a firstdirection causes rotation of the fourth link about the fifth axis in asecond direction; wherein one of the third or fourth actuators isconfigured and arranged to drive rotation of the element about the firstaxis when the other of the third or fourth actuator is operativelylocked. The first, second, third or fourth actuators may be configuredand arranged to drive rotation of the element about the first axis whenthe others of the first, second, third and fourth actuators have failedopen. The third link and the fourth link may be coupled (360) such thatthe first direction of rotation of the third link is opposite to thesecond direction of rotation of the fourth link. The third link and thefourth link may be coupled (260′) such that the first direction ofrotation of the third link is the same as the second direction ofrotation of the fourth link. Each of the actuators may be supported by abearing (436). The first actuator may comprise a planetary gear stage(600). The linkage system may comprise at least five links. The linkagesystem may comprise a plurality of pivot joints between the links. Thefirst actuator may comprise a rotary actuator. The first actuator maycomprise a rotary motor, a hydraulic actuator, or an electric motor. Thefirst link may comprise a stator and the second link may comprise astator. Each of the actuators may comprise a brake. The actuator systemmay further comprise a brake (603) configured and arranged to hold oneof the degrees of freedom of the linkage system constant. The actuatorsystem may further comprise a spring (604) configured and arranged tobias one of the degrees of freedom of the linkage system. The spring maybe selected from a group consisting of a torsional spring, a linearspring, and a flexure. The actuator system may further comprise a damper(605) configured and arranged to dampen rotation of at least one link inthe linkage system. The damper may be selected from a group consistingof a linear damper and a rotary damper. The first actuator and thesecond actuator may comprise a stepper motor or a permanent magnetmotor. The first actuator and the second actuator may comprise amagnetic clutch (607). The element may be selected from a groupconsisting of a shaft and an aircraft control surface. The element maybe selected from a group consisting of a wing spoiler, a flap, aflaperon and an aileron. The reference structure may be selected from agroup consisting of an actuator frame, an actuator housing and anairframe.

In another aspect, an actuator system (100′, 200′) is providedcomprising: a controlled element (180, 280) configured for rotarymovement about a first axis (105, 203) relative to a reference structure(110, 210); a linkage system (170, 270) connected to the element and thereference structure; a first actuator (120, 220) configured and arrangedto power a first degree of freedom of the linkage system (123 relativeto 122, 223 relative to 222); a hold device (140′, 240′) configured andarranged to selectively lock a second degree of freedom of the linkagesystem (143′ relative to 142′, 243′ relative to 242′), the first degreeof freedom and the second degree of freedom being independent degrees offreedom; the linkage system having a first link (123, 223) configuredfor rotary movement about a second axis (104, 204) relative to thereference structure; the first axis and the second axis not beingcoincident; the linkage system having a second link (143′, 243′)configured for rotary movement about a third axis (105, 205) relative tothe reference structure; the first link and the second link coupled(160, 260) such that rotation of the first link about the second axis ina first direction (126, 146, 226, 246) causes rotation of the secondlink about the third axis in a second direction (126, 146, 226, 246);the linkage system configured and arranged such that a first angle ofrotation (144, 244) between the element and the reference structure maybe driven independently of a second angle of rotation (125, 225) betweenthe first link and the reference structure; wherein the hold device isconfigured and arranged to lock the second degree of freedom when thefirst actuator is operational and to unlock the second degree of freedomwhen the first actuator is operatively locked.

The first axis (105, 203) and the second axis (104, 204) may besubstantially parallel and operatively offset a substantially constantdistance. The first axis (203), the second axis (204) and the third axis(205) may be substantially parallel and operatively offset asubstantially constant distance. The third axis may be substantiallycoincident with the second axis (104). The first link and the secondlink may be coupled (160, 260) such that the first direction of rotation(126, 226) of the first link is opposite to the second direction ofrotation (146, 246) of the second link. The first link and the secondlink may be coupled (260′) such that the first direction of rotation(226′) of the first link is the same as the second direction of rotation(226′) of the second link. The actuator system may further comprising: asecond actuator (320) configured and arranged to power a third degree offreedom of the linkage system (323 relative to 322); a second holddevice (340′) configured and arranged to selectively lock a fourthdegree of freedom of the linkage system (343′ relative to 342′), thethird degree of freedom and the fourth degree of freedom beingindependent degrees of freedom; the linkage system having a third link(323) configured for rotary movement about a fourth axis (304) relativeto the reference structure; the linkage system having a fourth link(343′) configured for rotary movement about a fifth axis (305) relativeto the reference structure; the fourth axis and the fifth axis not beingcoincident with each other or with the first axis or the second axis;the third link and the fourth link coupled (360) such that rotation ofthe third link about the fourth axis in a first direction causesrotation of the fourth link about the fifth axis in a second direction;wherein the second hold device is configured and arranged to lock thefourth degree of freedom when the second actuator is operational and tounlock the fourth degree of freedom when the second actuator isoperatively locked. The first actuator may comprise a rotary actuator.The first link may comprise a stator. The element may be selected from agroup consisting of a shaft and an aircraft control surface. Thereference structure may be selected from a group consisting of anactuator frame, an actuator housing and an airframe.

In another aspect, an actuator system (100, 200) is provided comprising:a controlled element (180, 280) configured for rotary movement about afirst axis (105, 203) relative to a reference structure (110, 210); aplurality of actuator units, each of the actuator units comprising: alinkage system (170, 270) connected to the element and the referencestructure; a first actuator (120, 220) configured and arranged to powera first degree of freedom of the linkage system (123 relative to 122,223 relative to 222); a second actuator (140, 240) configured andarranged to power a second degree of freedom of the linkage system (143relative to 142, 243 relative to 242), the first degree of freedom andthe second degree of freedom being independent degrees of freedom; thelinkage system having a first link (123, 223) configured for rotarymovement about a second axis (104, 204) relative to the referencestructure; the first axis and the second axis not being coincident; thelinkage system having a second link (143, 243) configured for rotarymovement about a third axis (105, 205) relative to the referencestructure; the first link and the second link coupled (160, 260) suchthat rotation of the first link about the second axis in a firstdirection (126, 146, 226, 246) causes rotation of the second link aboutthe third axis in a second direction (126, 146, 226, 246); the linkagesystem configured and arranged such that a first angle of rotation (144,244) between the element and the reference structure may be drivenindependently of a second angle of rotation (125, 225) between the firstlink and the reference structure; wherein one of the first or secondactuators is configured and arranged to drive rotation of the elementabout the first axis when the other of the first or second actuator isoperatively locked.

In another aspect, an actuator system (100, 200) is provided comprising:a controlled element (180, 280) configured for rotary movement about afirst axis (105, 203) relative to a reference structure (110, 210); aplurality of actuator units, each of the actuator units comprising: afirst actuator (120, 220) configured and arranged to power a firstdegree of freedom of the linkage system (123 relative to 122, 223relative to 222); a hold device (140′, 240′) configured and arranged toselectively lock a second degree of freedom of the linkage system (143′relative to 142′, 243′ relative to 242′), the first degree of freedomand the second degree of freedom being independent degrees of freedom;the linkage system having a first link (123, 223) configured for rotarymovement about a second axis (104, 204) relative to the referencestructure; the first axis and the second axis not being coincident; thelinkage system having a second link (143′, 243′) configured for rotarymovement about a third axis (105, 205) relative to the referencestructure; the first link and the second link coupled (160, 260) suchthat rotation of the first link about the second axis in a firstdirection (126, 146, 226, 246) causes rotation of the second link aboutthe third axis in a second direction (126, 146, 226, 246); the linkagesystem configured and arranged such that a first angle of rotation (144,244) between the element and the reference structure may be drivenindependently of a second angle of rotation (125, 225) between the firstlink and the reference structure; wherein the hold device is configuredand arranged to lock the second degree of freedom when the firstactuator is operational and to unlock the second degree of freedom whenthe first actuator is operatively locked.

In another aspect, an actuator system is provided comprising: areference structure; an output member rotatably coupled to the referencestructure for rotation about a first axis; a first actuator having afirst member and a second member, the second member configured to rotaterelative to the reference structure, the first member configured torotate relative to the reference structure about a second axis, thefirst member configured to rotate relative to the reference structureindependent of the rotation of the second member relative to thereference structure; a second actuator having a first member and asecond member, the second member configured to rotate relative to thereference structure, the first member configured to rotate relative tothe reference structure about a third axis, the first member configuredto rotate relative to the reference structure independent of therotation of the second member relative to the reference structure; afirst link pivotally connected between the first member of the firstactuator and the first member of the second actuator, the first memberof the first actuator and the first member of the second actuatorcoupled such that rotation of the first member of the first actuator ina first direction causes rotation of the first member of the secondactuator in a second direction; a second link pivotally connectedbetween the second member of the first actuator and the output member.

The actuator system may further comprise a third link pivotallyconnected between the second member of the second actuator and theoutput member. The first direction and the second direction may be thesame. The first direction and the second direction may be opposite. Thefirst axis and the third axis may be coincident. The first member may bea stator. The second member may be a rotor.

In another aspect, an actuator system is provided comprising: areference structure; an output member rotatably coupled to the referencestructure for rotation about a first axis; a first actuator having afirst member and a second member, the second member configured to rotaterelative to the reference structure, the first member configured torotate relative to the reference structure about a second axis, thefirst member configured to rotate relative to the reference structureindependent of the rotation of the second member relative to thereference structure; a holding device having a first member and a secondmember, the second member configured to rotate relative to the referencestructure, the holding device configured to alternate between a firstconfiguration where the rotational position of the first member relativeto the second member is locked and a second position where the first andsecond members are free to rotate relative to each other; a first linkpivotally connected between the first member of the first actuator andthe first member of the holding device, the first member of the firstactuator and the first member of the holding device coupled such thatrotation of the first member of the first actuator in a first directioncauses rotation of the first member of the holding device in a seconddirection; a second link pivotally connected between the second memberof the first actuator and the output member; wherein the holding devicemoves from the first configuration to the second configuration when thefirst actuator is operatively locked.

The actuator system may further comprise a third link pivotallyconnected between the second member of the holding device and the outputmember. The holding device may be a magnetic clutch. The first directionand the second direction may be the same. The first direction and thesecond direction may be opposite. The first axis and the third axis maybe coincident. The first member may be a stator. The second member maybe a rotor.

In another aspect, a method of controlling an actuator system isprovided comprising the steps of: providing an actuator systemcomprising: a controlled element configured for rotary movement about afirst axis relative to a reference structure; a linkage system connectedto the element and the reference structure; a first actuator configuredand arranged to power a first degree of freedom of the linkage system; asecond actuator configured and arranged to power a second degree offreedom of the linkage system, the first degree of freedom and thesecond degree of freedom being independent degrees of freedom; thelinkage system having a first link configured for rotary movement abouta second axis relative to the reference structure; the first axis andthe second axis not being coincident; the linkage system having a secondlink configured for rotary movement about a third axis relative to thereference structure; the first link and the second link coupled suchthat rotation of the first link about the second axis in a firstdirection causes rotation of the second link about the third axis in asecond direction; the linkage system configured and arranged such that afirst angle of rotation between the element and the reference structuremay be driven independently of a second angle of rotation between thefirst link and the reference structure; wherein one of the first orsecond actuators is configured and arranged to drive rotation of theelement about the first axis when the other of the first or secondactuator is operatively locked; and providing power to the firstactuator and the second actuator simultaneously such that the controlledelement is rotated about the second axis and an angular position of thefirst link is held constant about the first axis.

In another aspect, a method of controlling an actuator system isprovided comprising the steps of: providing an actuator systemcomprising: a controlled element configured for rotary movement about afirst axis relative to a reference structure; a linkage system connectedto the element and the reference structure; a first actuator configuredand arranged to power a first degree of freedom of the linkage system; ahold device configured and arranged to selectively lock a second degreeof freedom of the linkage system, the first degree of freedom and thesecond degree of freedom being independent degrees of freedom; thelinkage system having a first link configured for rotary movement abouta second axis relative to the reference structure; the first axis andthe second axis not being coincident; the linkage system having a secondlink configured for rotary movement about a third axis relative to thereference structure; the first link and the second link coupled suchthat rotation of the first link about the second axis in a firstdirection causes rotation of the second link about the third axis in asecond direction; the linkage system configured and arranged such that afirst angle of rotation between the element and the reference structuremay be driven independently of a second angle of rotation between thefirst link and the reference structure; wherein the hold device isconfigured and arranged to lock the second degree of freedom when thefirst actuator is operational and to unlock the second degree of freedomwhen the first actuator is operatively locked; and providing power tothe first actuator and the hold device simultaneously such that the holddevice link locks the second degree of freedom of the linkage system,and the first actuator applies a desired torque to the controlledelement

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a first actuator system.

FIG. 2 is an isometric view of an alternate embodiment of the firstactuator system.

FIG. 3 is a perspective view of a second actuator system.

FIG. 4 is a perspective view of an alternate embodiment of the secondactuator system.

FIG. 5 is a perspective view of a third actuator system.

FIG. 6 is an alternate embodiment of the third actuator system.

FIG. 7 is an alternate embodiment of the second actuator system.

FIG. 8 is a front perspective view of a fourth actuator system.

FIG. 9 is a rear perspective view of the fourth actuator system.

FIG. 10 is a front elevational view of the fourth actuator system.

FIG. 11 is a side elevational view of the fourth actuator system.

FIG. 12 is a sectional view taken along lines 12-12 of FIG. 11.

FIG. 13 is a rear elevational view of the fourth actuator system.

FIG. 14 is a partially exploded front perspective view of the fourthactuator system.

FIG. 15 is a partially exploded rear perspective view of the fourthactuator system.

FIG. 16 is a front perspective view of the fourth actuator system with areference structure removed for clarity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

At the outset, it should be clearly understood that like referencenumerals are intended to identify the same structural elements, portionsor surfaces consistently throughout the several drawing figures, as suchelements, portions or surfaces may be further described or explained bythe entire written specification, of which this detailed description isan integral part. Unless otherwise indicated, the drawings are intendedto be read (e.g., cross-hatching, arrangement of parts, proportion,debris, etc.) together with the specification, and are to be considereda portion of the entire written description of this invention. As usedin the following description, the terms “horizontal”, “vertical”,“left”, “right”, “up” and “down”, as well as adjectival and adverbialderivatives thereof, (e.g., “horizontally”, “rightwardly”, “upwardly”,etc.), simply refer to the orientation of the illustrated structure asthe particular drawing figure faces the reader. Similarly, the terms“inwardly” and “outwardly” generally refer to the orientation of asurface relative to its axis of elongation, or of rotation, asappropriate.

Referring now to the drawings, and initially to FIG. 1 thereof, thisinvention provides an improved actuator system, of which a firstembodiment is generally indicated at 100. Reference structure 110 maycomprise a rigid material. Reference structure 110 has a first portion110A and a second portion 110B, which are rigidly connected to eachother through a third portion 110C. First portion 110A holds twocouplings 112 and 113, which are connected to shaft 121 and shaft 141respectively. Coupling 112 holds shaft 121 in rotary engagement forrotation relative to reference structure 110 about axis 104. Similarly,coupling 113 holds shaft 141 in rotary engagement for rotation relativeto reference structure 110 about axis 105. Axes 104 and 105 aregenerally parallel to each other and separated by a fixed distance.

First rotary actuator 120 has a first member 123 and a second member 122which are configured and arranged for relative rotary motion to eachother about axis 104. Rotary actuator 120 is an electric motor, howeverother actuator types such as, but not limited to, hydraulic actuators,pneumatic actuators, or other similar actuators may also be used. Firstmember 123 may be referred to as a stator and second member 122 may bereferred to as a rotor, however, it should be noted that neither stator123 nor rotor 122 are stationary relative to reference structure 110.

Rotor 122 is rigidly coupled to shaft 121. Stator 123 is specificallynot rigidly mounted to reference structure 110. More concretely, stator123 is able to rotate relative to reference structure 110 about axis 104independent of the rotation of rotor 122 relative to reference structure110. Stated another way, first rotary actuator 120 has two degrees offreedom relative to reference structure 110. A first degree of freedomcan be defined as angle of rotation 124 of rotor 122 relative toreference structure 110. A second degree of freedom can be defined asangle of rotation 125 of stator 123 relative to reference structure 110.

Second rotary actuator member 140 has first member 143 and second member142 which are configured and arranged for relative rotary motion to eachother about axis 105. Rotary actuator 140 is an electric motor, howeverother actuator types such as, but not limited to hydraulic actuators,pneumatic actuators, or other similar actuators may also be used. Firstmember 143 may be referred to as a stator and second member 142 may bereferred to as a rotor. However, it should be noted that neither stator143 nor rotor 142 are stationary relative to reference structure 110.

Rotor 142 is rigidly coupled to shaft 141. Stator 143 is specificallynot rigidly mounted to reference structure 110. More concretely, stator143 is able to rotate relative to reference structure 110 about axis 105independent the rotation of rotor 142 relative to the referencestructure 110. Stated another way, second actuator 140 has two degreesof freedom relative to reference structure 110. A first degree offreedom can be defined as angle of rotation 144 of rotor 142 relative toreference structure 110. A second degree of freedom can be defined asangle of rotation 145 of stator 123 relative to reference structure 110.

Output member 180 is rigidly coupled to rotor 142. Therefore, outputmember rotates together with rotor 142 relative to reference structure110 about axis 105. Second portion 110B of reference structure 110 hascouplings 115 and 116 which respectively provide additional support inholding output member 180 and rotor 122 in rotary engagement withreference structure 110. Output member 180 may be coupled to an objectto be driven, such as an aircraft control surface.

Stator 123 and stator 143 are rotationally coupled together throughcoupling 160. Coupling 160 causes stator 123 to rotate relative toreference structure 110 by an angle opposite to the rotation of stator143 relative to reference structure 110. More specifically, coupling 160causes any change in angle 125 to cause an equal and opposite change inangle 145. In other words, a degree of freedom between rotary actuator120 and reference structure 110 is caused to be shared with one degreeof freedom between rotary actuator 140 and reference structure 110 bycoupling 160. Coupling 160 is a link pivotally connected to stator 123and pivotally connected to stator 143. Drive arm portion 123 a isdisposed on stator 123, and drive arm portion 143 a is disposed onstator 143. Link 160 a is pivotally connected between drive arm portions123 a and 143 a. However, coupling 160 my alternatively be a gearcoupling, a belt coupling, or other similar coupling.

Rotor 122 and rotor 142 are also coupled together through coupling 190.Coupling 190 causes rotor 122 to rotate relative to reference structure110 by an angular direction equal to how rotor 142 rotates relative toreference structure 110. More specifically, coupling 190 causes anychange in angle 124 to equal a change in angle 144. In other words, adegree of freedom between rotary actuator 120 and reference structure110 is caused to be shared with one degree of freedom between rotaryactuator 140 and reference structure 110 by coupling 190. As shown inFIG. 1, coupling 190 is a link 190 a pivotally connected to drive armportion 122A of member 122 and pivotally connected to drive arm portion142A of member 142, however, coupling 190 my alternatively be a gearcoupling, a belt coupling, or other similar coupling.

While coupling 160 causes stator 123 and stator 143 to rotate inopposite directions relative to reference structure 110, coupling 190causes rotor 122 and rotor 142 to rotate in equivalent directionsrelative to reference structure 110.

Linkage 170 is a set of rigid links and joints between reference member110 and output member 180. More specifically, linkage 170 comprisescouplings 160 and 190, and members 121, 122, 123, 141, 142, and 143.Linkage 170 has two degrees of freedom relative to reference 110. Inother words, the state of linkage 170 relative to reference 110 can bedescribed by two independent variables. For example, knowing angle 144(which represents the angle of rotor 142 to reference structure 110) andangle 124 (the angle of shaft 121 relative to reference structure 110)specifically define the state of linkage 170 since no member (link)within linkage 170 can be moved without adjusting angles 144 or 124. Inthis view, angle 124 and angle 144 represent two independent degrees offreedom of linkage 170. Alternatively, the two degrees of freedom oflinkage 170 can be defined as angle 125 and angle 144. No linkage 170member can be moved relative to linkage 110 without changing angle 125or angle 144.

Rotary actuator 100 is generally operated by powering first actuator 120and second actuator 140 together at the same time to cause output member180 to move relative to reference structure 110 in a desired manner. Forexample, if a user desires to cause output member 180 to rotateclockwise relative to reference structure 110, in other words, if angle144 is to be decreased, actuator 120 and actuator 140 would be actuatedat the same time, actuator 120 providing a torque of equal and oppositemagnitude as actuator 140. More specifically, actuator 120 is actuatedso as to apply a torque urging rotor 122 to rotate clockwise relative tostator 123. At the same time, actuator 140 is actuated so as to apply atorque urging rotor 142 to rotate clockwise relative to stator 143.Under this scenario, counteracting torques from actuator 120 andactuator 140 act against each other through coupling 160. When actuator120 applies a torque to rotor 122 in the clockwise direction, an equaland opposite torque is applied to coupling 160, urging coupling 160 torotate counterclockwise. The torque applied by actuator 120 ontocoupling 160 manifests as a downward rightwards force on coupling 160.When actuator 140 applies a torque to rotor 142 in the clockwisedirection, an equal and opposite torque is applied to coupling 160. Thetorque applied by actuator 140 onto coupling 160 manifests as anupwards-leftwards force applied on coupling 160 by actuator 140. Theforce applied by actuator 120 onto coupling 160 is generally equal andopposite the force applied by actuator 140 onto coupling 160. Thisgenerally results in stators 123 and 143 remaining stationary whilerotors 122 and 142 rotate clockwise. Coupling 190 causes the angles ofrotation 124, 144 of rotors 122 and 142 relative to reference structure110 to remain equivalent.

In order to cause output member 180 to rotate counter clockwise relativeto reference structure 110, rotary actuators 120 and 140 are actuated inthe reverse direction compared to when causing output member 180 torotate clockwise.

Actuator 100 has the advantageous characteristic that if either actuator120 or actuator 140 lock up (such as an electromechanical jam, orhydraulic valve lock), output member 180 will continue to be actuated inthe desired direction of rotation by the non-failing actuator. This isbecause the locked up actuator will still be able to provide acounteracting torque to the other actuator through coupling 160. Forexample, consider a user desiring to rotate output member 180 clockwiserelative to reference structure 110 (decreasing angle 144) when actuator120 inadvertently rotationally locks stator 123 relative to rotor 122.Because stator 123 is rotationally locked to rotor 122, any change inangle 124 between rotor 122 and reference structure 110 will necessaryequal any change in angle 125 between stator 123 and reference structure110. Note that stator 123 and rotor 122 may still rotate together as aunit relative to reference structure 110. When actuator 140 applies aclockwise torque to rotor 142, the equal and opposite torque on stator143 is distributed through coupling 160 as an upwards and leftwardsforce on coupling 160. This upwards and leftwards force on coupling 160results in a clockwise torque applied to stator 123 which is transmittedthrough the locked up actuator as a clockwise torque onto rotor 122.Coupling 190 causes the rotation of rotors 122 and 142 to be equalized,while output member 180 is rotated clockwise as desired through the jam.

In order to operate in a dual tandem mode, each actuator 120, 140 isprovided with a braking mechanism which may be internal or external anda controller. These brakes will allow the actuator system 100 tocontinue working if one of the actuators fails in an open state (e.g. anactuator loses power allowing the stator and rotor free rotationrelative to each other). The brake is configured within each actuator tolock rotation between the actuators stator and rotor relative to eachother. The brake may be a fail-safe brake which does not need power inorder to brake. In this dual tandem configuration, when one of theactuators 120, 140 fails in an open state, the brake in that failingactuator is engaged. This allows the remaining actuator 120, 140 tostill cause actuation of output member 180. However, during such afailure the speed that output member 180 rotates relative to the workingactuator will be half the speed that the output member 180 rotates atwhen both actuators are working.

Turning to FIG. 2, which shows an alternate embodiment 100′, actuator120 is paired with a holding device 140′ which includes, but is notlimited to, a brake, a magnetic clutch, a toroid motor, or the like.Under normal operation, holding device 140′ locks the rotational positonbetween member 143′ and member 142′. If the actuator 120 jams then theholding device 140′ releases the lock between member 143′ and member142′ which effectively releases any effect actuator 120 has on outputmember 180. This allows output member 180 to be driven by anotheractuator (not shown). This arrangement is a simplex configurationbecause it includes one actuator 120 and one holding device 140′ and ifthe actuator 120 fails, the unit drops out of the network as will bedescribed in greater detail below. In yet another alternate simplexconfiguration, two actuators may be provided without any brakes oneither actuator, where one actuator is configured to only hold its rotorand stator position, while the other actuator is used to drive outputmember 180 through linkage system 170.

In FIG. 3, a second actuator system is generally indicated at 200.Reference structure 210 comprises a rigid material. Reference structure210 has a first portion 210A and a second portion 210B, which are fixed.First portion 210A holds two couplings 212 and 213, which are connectedto shaft 221 and shaft 241 respectively. Coupling 212 holds shaft 221 inrotary engagement for rotation relative to reference structure 210 aboutaxis 204. Similarly, coupling 213 holds shaft 241 in rotary engagementfor rotation relative to reference structure 210 about axis 205. Axes204 and 205 are generally parallel to each other and separated by afixed distance.

First rotary actuator 220 has a first member 223 and a second member 222which are configured and arranged for relative rotary motion to eachother about axis 204. Rotary actuator 220 is an electric motor, howeverother actuator types such as, but not limited to, hydraulic actuators,pneumatic actuators, or other similar actuators may also be used. Firstmember 223 may be referred to as a stator and second member 222 may bereferred to as a rotor, however, it should be noted that neither stator223 nor rotor 222 are stationary relative to reference structure 210.

Rotor 222 is rigidly coupled to shaft 221. Stator 223 is specificallynot rigidly mounted to reference structure 210. More concretely, stator223 is able to rotate relative to reference structure 210 about axis 204independent of the rotation of rotor 222 relative to reference structure210. Stated another way, first rotary actuator 220 has two degrees offreedom relative to reference structure 210. A first degree of freedomcan be defined as angle of rotation 224 of rotor 122 relative toreference structure 210. A second degree of freedom can be defined asangle of rotation 225 of stator 223 relative to reference structure 210.

Second rotary actuator member 240 has first member 243 and second member242 which are configured and arranged for relative rotary motion to eachother about axis 205. Rotary actuator 240 is an electric motor, howeverother actuator types such as, but not limited to hydraulic actuators,pneumatic actuators, or other similar actuators may also be used. Firstmember 243 may be referred to as a stator and second member 242 may bereferred to as a rotor. However, it should be noted that neither stator243 nor rotor 242 are stationary relative to reference structure 210.

Rotor 242 is rigidly coupled to shaft 241. Stator 243 is specificallynot rigidly mounted to reference structure 210. More concretely, stator243 is able to rotate relative to reference structure 210 about axis 205independent the rotation of rotor 242 relative to the referencestructure 210. Stated another way, second actuator 240 has two degreesof freedom relative to reference structure 210. A first degree offreedom can be defined as angle of rotation 244 of rotor 242 relative toreference structure 210. A second degree of freedom can be defined asangle of rotation 245 of stator 223 relative to reference structure 210.

Output member 280 is coupled to rotors 222, 242. Therefore, outputmember 280 rotates together with rotors 222, 242 relative to referencestructure 210. Second portion of 210B reference structure 210 hascouplings 215 and 216 which respectively provide additional support inholding rotors 222, 242 in rotary engagement with reference structure210. Couplings 214, 219 hold output member 280 in rotary engagement forrotation relative to reference structure 210. Output member 280 may becoupled to an object to be driven, such as an aircraft control surface.

Stator 223 and stator 243 are rotationally coupled together throughcoupling 260. Coupling 260 causes stator 223 to rotate relative toreference structure 210 by an angle opposite to the rotation of stator243 relative to reference structure 210. More specifically, coupling 260causes any change in angle 225 to cause an equal and opposite change inangle 245. In other words, a degree of freedom between rotary actuator220 and reference structure 210 is caused to be shared with one degreeof freedom between rotary actuator 240 and reference structure 210 bycoupling 260. Coupling 260 is a link 260 a pivotally connected to drivearm portion 223 a of stator 223 and pivotally connected to drive armportion 243 a of stator 243. However, coupling 260 may alternatively bea gear coupling, a belt coupling, or other similar coupling.

Rotor 222 and rotor 242 are both coupled to output member 280 throughcoupling 270. Coupling 270 causes the rotation of both rotors 222 and242 to be transmitted to the output member 280 such that the outputmember 280 rotates in the same direction as the rotors 222, 242 relativeto the reference structure 210. More specifically, coupling 270 causesthe rotation of the rotors 222, 242 to be summed together at the outputmember 280. Coupling 270 comprises a pair of links 270 a and 270 b. Link270 a is pivotally connected between drive arm portion 222A of member222 and drive arm portion 280 a of output member 280. Link 270 b ispivotally connected between drive arm portion 242A of member 242 anddrive arm portion 280 b of output member 280. However, coupling 270 mayalternatively be a gear coupling, a belt coupling, or other similarcoupling.

While coupling 260 causes stator 223 and stator 243 to rotate inopposite directions relative to reference structure 210, coupling 270causes rotor 122 and rotor 142 to rotate in equivalent directionsrelative to reference structure 210.

Linkage 290 is a set of rigid links and joints between reference member210 and output member 280. More specifically, linkage 290 comprisescouplings 260 and 270, and members 221, 222, 223, 241, 242, and 243.Linkage 290 has two degrees of freedom relative to reference 210. Inother words, the state of linkage 290 relative to reference 210 can bedescribed by two independent variables. For example, knowing angle 244(which represents the angle of rotor 242 to reference structure 210) andangle 224 (the angle of shaft 221 relative to reference structure 210)specifically define the state of linkage 290 since no member (link)within linkage 290 can be moved without adjusting angles 244 or 224. Inthis view, angle 224 and angle 244 represent two independent degrees offreedom of linkage 290. Alternatively, the two degrees of freedom oflinkage 290 can be defined as angle 225 and angle 244. No linkage 290member can be moved relative to linkage 210 without changing angle 225or angle 244.

Rotary actuator 200 is generally operated by powering first actuator 220and second actuator 240 together at the same time to cause output member280 to move relative to reference structure 210 in a desired manner. Forexample, if a user desires to cause output member 280 to rotateclockwise relative to reference structure 210 (as shown in the apparatusorientation in FIG. 2), actuator 220 and actuator 240 would be actuatedat the same time, actuator 220 providing a torque of equal and oppositemagnitude as actuator 240. More specifically, actuator 220 is actuatedso as to apply a torque urging rotor 222 to rotate clockwise relative tostator 223. At the same time, actuator 240 is actuated so as to apply atorque urging rotor 242 to rotate clockwise relative to stator 243.Under this scenario, counteracting torques from actuator 220 andactuator 240 act against each other through coupling 260. Morespecifically, when actuator 220 applies a torque to rotor 222 in theclockwise direction, an equal and opposite torque is applied to coupling260, urging coupling 260 to rotate counterclockwise. The torque appliedby actuator 220 onto coupling 260 manifests as a downward rightwardsforce on coupling 260. When actuator 240 applies a torque to rotor 242in the clockwise direction, an equal and opposite torque is applied tocoupling 260. The torque applied by actuator 240 onto coupling 260manifests as an upwards-leftwards force applied on coupling 260 byactuator 240. The force applied by actuator 220 onto coupling 260 isgenerally equal and opposite the force applied by actuator 240 ontocoupling 260. This generally results in stators 223 and 243 remainingstationary while rotors 222 and 242 rotate clockwise. Coupling 270causes the angles of rotation 224, 244 of rotors 222 and 242 relative toreference structure 210 to remain equivalent.

In order to cause output member 280 to rotate counter clockwise relativeto reference structure 210, rotary actuators 220 and 240 are actuated inreverse compared to when causing output member 280 to rotate clockwise.

In order to operate in a dual tandem mode, each actuator 220, 240 isprovide with a brake that may be internal or external and a controller.If one of the actuators 220, 240 loses power then the brake in thefailing unit will be applied, allowing the remaining actuator 220, 240to move the output member at one half normal speed. Actuator 200 alsohas the advantageous characteristic that if either actuator 220 oractuator 240 lock up (such as an electromechanical jam, or hydraulicvalve lock), output member 280 will continue to be actuated in thedesired direction of rotation by the non-failing actuator. This isbecause the locked up actuator will still be able to provide acounteracting torque to the other actuator through coupling 260. Forexample, consider a user desiring to rotate output member 280 clockwiserelative to reference structure 210 when actuator 220 inadvertentlyrotationally locks stator 223 relative to rotor 222. Because stator 223is rotationally locked to rotor 222, any change in angle 224 betweenrotor 222 and reference structure 210 will necessary equal any change inangle 225 between stator 223 and reference structure 210. Note thatstator 223 and rotor 222 may still rotate together as a unit relative toreference structure 210. When actuator 240 applies a clockwise torque torotor 242, the equal and opposite torque on stator 243 is distributedthrough coupling 260 as an upwards and leftwards force on coupling 260.This upwards and leftwards force on coupling 260 results in a clockwisetorque applied to stator 223 which is transmitted through the locked upactuator as a clockwise torque onto rotor 2122. Coupling 270 causes therotation of rotors 222 and 242 to be equalized, while output member 280is rotated clockwise as desired through the jam.

Turning to FIG. 4, the actuator 220 is paired with holding device 240′which includes, but is not limited to, a brake, a magnetic clutch, atoroid motor or the like. Under normal operation, holding device 240′locks member 243′ and rotor 242′ relative to each other. If the actuator220 jams or loses power then the holding device 240′ releases the rotor242′ and the actuator 220 and hold device 240′ go into a bypass mode androtate freely under the power of another actuator in the network. In yetanother simplex configuration, actuators 220 and 240 of FIG. 3 may beprovided without any brakes.

Turning to FIG. 5, a system with dual tandem actuators 220 and 240 ispaired with dual tandem actuators 320 and 340 to form a third actuatorsystem generally indicated at 300. Reference structure 310 comprises arigid material. Reference structure 310 has a first portion 310A and asecond portion 310B, which are fixed. First portion 310A holds twocouplings 312 and 313, which are connected to shaft 321 and shaft 341respectively. Coupling 312 holds shaft 321 in rotary engagement forrotation relative to reference structure 310 about axis 304. Similarly,coupling 313 holds shaft 341 in rotary engagement for rotation relativeto reference structure 310 about axis 305. Axes 304 and 305 aregenerally parallel to each other and separated by a fixed distance.

First rotary actuator 320 has a first member 323 and a second member 322which are configured and arranged for relative rotary motion to eachother about axis 304. Rotary actuator 320 is an electric motor, howeverother actuator types such as, but not limited to, hydraulic actuators,pneumatic actuators, or other similar actuators may also be used. Firstmember 323 may be referred to as a stator and second member 322 may bereferred to as a rotor, however, it should be noted that neither stator323 nor rotor 322 are stationary relative to reference structure 310.

Rotor 322 is rigidly coupled to shaft 321. Stator 323 is specificallynot rigidly mounted to reference structure 310. More concretely, stator323 is able to rotate relative to reference structure 310 about axis 304independent of the rotation of rotor 322 relative to reference structure310. Stated another way, first rotary actuator 320 has two degrees offreedom relative to reference structure 310. A first degree of freedomcan be defined as angle of rotation 324 of rotor 322 relative toreference structure 310. A second degree of freedom can be defined asangle of rotation 325 of stator 323 relative to reference structure 310.

Second rotary actuator member 340 has first member 343 and second member342 which are configured and arranged for relative rotary motion to eachother about axis 305. Rotary actuator 340 is an electric motor, howeverother actuator types such as, but not limited to hydraulic actuators,pneumatic actuators, or other similar actuators may also be used. Firstmember 343 may be referred to as a stator and second member 342 may bereferred to as a rotor. However, it should be noted that neither stator343 nor rotor 342 are stationary relative to reference structure 310.

Rotor 342 is rigidly coupled to shaft 341. Stator 343 is specificallynot rigidly mounted to reference structure 310. More concretely, stator343 is able to rotate relative to reference structure 310 about axis 305independent the rotation of rotor 342 relative to the referencestructure 310. Stated another way, second actuator 340 has two degreesof freedom relative to reference structure 310. A first degree offreedom can be defined as angle of rotation 344 of rotor 342 relative toreference structure 310. A second degree of freedom can be defined asangle of rotation 345 of stator 323 relative to reference structure 310.

Output member 280 is coupled to rotors 322, 342. Therefore, outputmember 280 rotates together with rotors 322, 342 relative to referencestructure 310. Second portion of 310B reference structure 310 hascouplings 315 and 316 which respectively provide additional support inholding rotors 322, 342 in rotary engagement with reference structure310. Output member 280 may be coupled to an object to be driven, such asan aircraft control surface.

Stator 323 and stator 343 are rotationally coupled together throughcoupling 360. Coupling 360 causes stator 323 to rotate relative toreference structure 310 by an angle opposite to the rotation of stator343 relative to reference structure 310. More specifically, coupling 360causes any change in angle 325 to cause an equal and opposite change inangle 345. In other words, a degree of freedom between rotary actuator320 and reference structure 310 is caused to be shared with one degreeof freedom between rotary actuator 340 and reference structure 310 bycoupling 360. Coupling 360 is a link 360 a pivotally connected to drivearm portion 323 a of stator 323 and pivotally connected to drive armportion 343 a of stator 343. However, coupling 360 may alternatively bea gear coupling, a belt coupling, or other similar coupling.

Rotor 322 and rotor 342 are both coupled to output member 280 throughcoupling 370. Coupling 370 causes the rotation of both rotors 322 and342 to be transmitted to the output member 280 such that the outputmember 280 rotates in the same direction as the rotors 322, 342 relativeto the reference structure 310. More specifically, coupling 370 causesthe rotation of the rotors 322, 342 to be summed together at the outputmember 280. Coupling 370 comprises a pair of links 370 a and 370 b. Link370 a is pivotally connected between drive arm portion 322A of member322 and drive arm portion 280 a of output member 280. Link 370 b ispivotally connected between drive arm portion 342 a of member 342 anddrive arm portion 280 b of output member 280. However, coupling 370 mayalternatively be a gear coupling, a belt coupling, or other similarcoupling.

While coupling 360 causes stator 323 and stator 343 to rotate inopposite directions relative to reference structure 310, coupling 370causes rotor 322 and rotor 342 to rotate in equivalent directionsrelative to reference structure 310.

Linkage 390 is a set of rigid links and joints between reference member310 and output member 280. More specifically, linkage 390 comprisescouplings 360 and 370, and members 321, 322, 323, 341, 342, and 343.Linkage 390 has two degrees of freedom relative to reference 310. Inother words, the state of linkage 390 relative to reference 310 can bedescribed by two independent variables. For example, knowing angle 344(which represents the angle of rotor 342 to reference structure 310) andangle 324 (the angle of shaft 321 relative to reference structure 310)specifically define the state of linkage 390 since no member (link)within linkage 390 can be moved without adjusting angles 344 or 324. Inthis view, angle 324 and angle 344 represent two independent degrees offreedom of linkage 390. Alternatively, the two degrees of freedom oflinkage 390 can be defined as angle 325 and angle 344. No linkage 390member can be moved relative to linkage 310 without changing angle 325or angle 344.

Rotary actuator 300 is generally operated by powering first actuator 320and second actuator 340 together at the same time to cause output member380 to move relative to reference structure 310 in a desired manner. Forexample, if a user desires to cause output member 280 to rotateclockwise relative to reference structure 310 (as shown in the apparatusorientation in FIG. 5), actuator 320 and actuator 340 would be actuatedat the same time, actuator 320 providing a torque of equal and oppositemagnitude as actuator 340. More specifically, actuator 320 is actuatedso as to apply a torque urging rotor 322 to rotate clockwise relative tostator 323. At the same time, actuator 340 is actuated so as to apply atorque urging rotor 342 to rotate clockwise relative to stator 343.Under this scenario, counteracting torques from actuator 320 andactuator 340 act against each other through coupling 360. Morespecifically, when actuator 320 applies a torque to rotor 322 in theclockwise direction, an equal and opposite torque is applied to coupling360, urging coupling 360 to rotate counterclockwise. The torque appliedby actuator 320 onto coupling 360 manifests as a downward rightwardsforce on coupling 360. When actuator 340 applies a torque to rotor 342in the clockwise direction, an equal and opposite torque is applied tocoupling 360. The torque applied by actuator 340 onto coupling 360manifests as an upwards-leftwards force applied on coupling 360 byactuator 340. The force applied by actuator 320 onto coupling 360 isgenerally equal and opposite the force applied by actuator 340 ontocoupling 360. This generally results in stators 323 and 343 remainingstationary while rotors 322 and 342 rotate clockwise. Coupling 370causes the angles of rotation 324, 344 of rotors 322 and 342 relative toreference structure 310 to remain equivalent.

In order to cause output member 280 to rotate counter clockwise relativeto reference structure 310, rotary actuators 320 and 340 are actuated inreverse compared to when causing output member 280 to rotate clockwise.

In order to operate in a dual tandem mode, each actuator 220, 240, 320,340 is provided with a brake that may be internal or external and acontroller. If one or more of the actuators 220, 240, 320, 340 losepower then one of the remaining actuators 220, 240, 320, 340 can movethe output member 280. The third actuator system 300 also has theadvantageous characteristic that if any of the actuators 220, 240, 320,340 lock up (such as an electromechanical jam, or hydraulic valve lock),output member 280 will continue to be actuated in the desired directionof rotation by at least one of the non-failing actuators. This isbecause, in the case of failure of actuator 220 or 240, the locked upactuator will still be able to provide a counteracting torque to theother actuator through coupling 260. For example, consider a userdesiring to rotate output member 280 clockwise relative to referencestructure 210 when actuator 220 inadvertently rotationally locks stator223 relative to rotor 222. Because stator 223 is rotationally locked torotor 222, any change in angle 224 between rotor 222 and referencestructure 210 will necessary equal any change in angle 225 betweenstator 223 and reference structure 210. Note that stator 223 and rotor222 may still rotate together as a unit relative to reference structure210. When actuator 240 applies a clockwise torque to rotor 242, theequal and opposite torque on stator 243 is distributed through coupling260 as an upwards and leftwards force on coupling 260. This upwards andleftwards force on coupling 260 results in a clockwise torque applied tostator 223 which is transmitted through the locked up actuator as aclockwise torque onto rotor 2122. Coupling 270 causes the rotation ofrotors 222 and 242 to be equalized, while output member 280 is rotatedclockwise as desired through the jam. Also, rotors 320, 340 continue torotate output member 280 in the clockwise direction.

Turning to FIG. 6, each of the actuators 220, 320 is paired with aholding device 240′ and 340′ for simplex unit operation as describedabove in connection with FIGS. 2 and 4.

In FIG. 7, coupling 260′ includes a link 260 a′ that pivotally connectsbetween drive arm portion 243 a of stator 243 and drive arm portion 223a of stator 223 at pivot points 290, 292. In contrast to the arrangementof coupling 260, the link 260 a′ does not cross a line 261′ between thecenters of axes 204 and 205. The coupling 270′ includes a link 270 a′pivotally connected between drive arm portion 242 a and drive portion280 a of output member 280 at pivot points 294, 295 and a link 270 b′pivotally connected between drive arm portion 222 a and drive portion280 b of output member 280 at pivot points 296, 297. The link 270 b′crosses over to the opposite side of axis 205.

Referring generally to FIGS. 8-11 and initially to FIG. 8, a fourthactuator system 400 includes six actuators 403, 406, 409, 412, 415 (FIG.9), and 418 (FIG. 9). The actuators are arranged with momentcancellation and are all mechanically coupled to a common output member421 (FIG. 12) as described in detail below. The actuators may bearranged in pairs that may be dual tandem or simplex pairs. In the caseof simplex pair units, one of the actuators in each pair is substitutedwith a holding device as described above. In the case of loss of poweror a jam for an actuator paired with a holding device, the unit dropsout of the network and freely rotates. In the case of a dual tandemunit, each actuator is provided with a brake that may be internal orexternal and a controller such that loss of power for one actuator ofthe pair results in the other actuator of the pair moving the tandemunit together.

Output member 421 is configured to engage with a shaft 424. As shown,the shaft 424 is a spline shaft, however, it will be evident to those ofordinary skill in the art based on this disclosure that other mechanicalmeans for transmitting rotation from the output member 421 may also beused. Reference structure 427 and reference structure 430 are rigidmembers. A link 433 is fixedly attached to the reference structures 427,430. Reference structure 430 includes bearing 431.

Starting at the bottom FIG. 8, and working counterclockwise, a momentcanceling arm 478 is connected to stator 439 of first actuator 403. Themoment canceling arm 478 rotates with the stator 439 about axis 481. Alink 484 is pivotally attached to arm 478 at one end and is pivotallyattached to a moment canceling arm 487 connected to the stator 442 ofactuator 406 which forms a pair with actuator 403. Continuingcounterclockwise, moment canceling arm 493 is connected to the stator445 of actuator 409. The link that connects arm 493 to its neighboringarm 496 has been removed for clarity. Moment canceling arm 496 isconnected to stator 448 of actuator 412. Moment canceling arm 499 isconnected to stator 451 of actuator 415. A link 502 is pivotallyattached to arm 499 at one end and is pivotally attached to arm 505 atthe opposite end. Arm 505 is connected to stator 454 of actuator 418.The rotors 457, 460, 463 etc. are disposed between reference structures427 and 430 and rotate relative to their respective stators. The rotorsare coupled to the output member 421 as described in detail below.

Reference structure 427 includes bearings 436 (best shown in FIG. 15)for holding Stators 439, 442, 445, 448, 451, and 454 (FIG. 13) in rotaryengagement for rotation relative to reference structure 427.

Turning to FIG. 12 rotors 457, 460, 463, 466, 469, 472 are configuredand arranged for rotary motion relative to their respective stators. Therotors 457, 460, 463, 466, 469, 472 are mechanically coupled to theoutput member 421. Starting at the bottom right hand side of FIG. 12 andmoving counterclockwise, drive arm portion 511 of rotor 457 rotates withthe rotor 457 about axis 514 normal to the page. A link 517 is pivotallyconnected to drive arm portion 511 at one end and is pivotally connectedto a crank 520 at the opposite end. The crank 520 is fixedly attached tothe output member 421. Drive arm portion 523 of rotor 460 rotates withrotor 460 about axis 526 normal to the page. A link 529 is pivotallyconnected to drive arm portion 523 at a first end and is pivotallyconnected to a crank 532 at a second end. The crank 532 is fixedlyattached to the output member 421 and is positioned below crank 520 withrespect to the orientation of FIG. 12. Drive arm portion 535 of rotor463 rotates with rotor 463 about axis 538 normal to the page. A link 541is pivotally connected to drive arm portion 535 at a first end and ispivotally connected to crank 520 at the opposite end. Drive arm portion544 of rotor 466 rotates with rotor 466 about axis 547 normal to thepage. A link 550 is pivotally connected to drive arm portion 544 at afirst end and is pivotally connected to crank 532 at the opposite end.Drive arm portion 553 of rotor 469 rotates with rotor 469 about axis 556normal to the page. A link 557 is pivotally connected to drive arm 553at a first end and is pivotally connected to crank 520 at the oppositeend. Drive arm 559 of rotor 472 rotates with rotor 472 about axis 562normal to the page. A link 565 is pivotally connected to the drive arm559 at a first end and is pivotally connected to crank 532 at theopposite end.

Turning to FIGS. 14 and 15, exploded perspective views show an actuator415. The actuator 415 includes a stator 451 which includes a torque tube452 connected to the moment canceling arm 499. All of the parts of thestator 451 are arranged for rotary motion relative to the referencestructures 427, 430 and are configured for relative rotation with itsrotor 469. Rotor 469 has a drive arm portion 553 that is connected tothe output member 421 as described above in connection with FIG. 12.Moment canceling arm 499 of stator 451 is connected to the momentcanceling arm 505 of an adjacent actuator 418 by means of link 502. Arms499 and 505 are coupled together such that their moment is canceled. Theremaining pairs of moment canceling arms 478 and 487 and 493 and 496 areconfigured the same way to form a network of three actuator units witheach unit comprising two actuators connected in the same manner.

In FIG. 16, the fourth actuator system 400 is shown with referencestructure 430 removed for clarity. At the left side of the figure, theconnection of the moment canceling drive arms 499 and 505 by means oflink 502 is shown. The link 502 is pivotally attached at a first end todrive arm 499 at pivot point 506 and is pivotally attached to drive arm505 at the opposite end at pivot point 507.

The output member 421 has a splined bore 422 for receiving a splinedshaft 424 (FIG. 8). The output member 421 may be provided with cranks520 and 532 (FIG. 12) that are coupled to the output member 421 suchthat forces on the cranks 520 and 532 cause the output member 421 torotate. Rotor 463 is connected to the crank 520 via a connecting rod orlink 541 that is pivotally attached to the drive arm portion 535 ofrotor 463 at a first end at pivot point 536 and is pivotally attached tothe crank 520 at the opposite end at pivot point 537. The crank 532 isbelow or to the right in the axial direction with respect to the axis550 of rotation of the output member 421. The crank 520 may be providedwith a generally triangular shape for connection to three of the rotorsand crank 532 may also be provided with a generally triangular shape forconnection to the three other rotors.

Several modifications can be made to the disclosed embodiments. Forexample, position sensors, resolvers, and/or encoders may be added toactuators and/or any other linkage joint in order to provide usefulfeedback to a controller. Additionally, torque sensors, and/ortachometers may additionally be added to each actuator output and/or anyother link joint in the linkage system to provide further feedback. Indual tandem configurations, one motor in a pair may be of a differenttype than its corresponding motor. For example, one motor may be a hightorque, high velocity motor, whereas the other motor may be a lowvelocity, high efficiency, high torque motor. Additionally inconfigurations in which multiple dual tandem pairs are used, brakes maybe safely removed since open actuator failures are not a major concernwhen a second pair of actuators is available to control the outputmember in the event of an open failure.

The disclosed embodiments resulted in several significant advantages.The multiply redundant nature of the disclosed configurations providehigh fail-safe statistical levels, especially in triplex configurations.Because there is an additional degree of freedom in each actuator pair,a self test may be safely conducted during use in which one actuatormoves relative to another actuator without changing the position of theoutput member. The hexagonal arrangement of the fourth system provides ahighly space efficient configuration which allows for arrangement intightly constrained vehicle frames such as in aircraft airframes.

Several actuator systems have been shown and described, and severalmodifications and alternatives have been discussed. Therefore, personsskilled in this art will readily appreciate that various additionalchanges and modifications may be made without departing from the spiritof the invention, as defined and differentiated by the following claims.

The invention claimed is:
 1. An actuator system comprising: a controlled element configured for rotary movement about a first axis relative to a reference structure; a linkage system connected to said element and said reference structure; a first actuator configured and arranged to power a first degree of freedom of said linkage system; a second actuator configured and arranged to power a second degree of freedom of said linkage system, said first degree of freedom and said second degree of freedom being independent degrees of freedom; said linkage system having a first link configured for rotary movement about a second axis relative to said reference structure; said first axis and said second axis not being coincident; said linkage system having a second link configured for rotary movement about a third axis relative to said reference structure; said first link and said second link coupled such that rotation of said first link about said second axis in a first direction causes rotation of said second link about said third axis in a second direction; said linkage system configured and arranged such that a first angle of rotation between said element and said reference structure may be driven independently of a second angle of rotation between said first link and said reference structure; wherein one of said first or second actuators is configured and arranged to drive rotation of said element about said first axis when said other of said first or second actuator is operatively locked.
 2. The actuator system as set forth in claim 1, wherein said first axis and said second axis are substantially parallel and operatively offset a substantially constant distance.
 3. The actuator system as set forth in claim 2, wherein said first axis, said second axis and said third axis are substantially parallel and operatively offset a substantially constant distance.
 4. The actuator system as set forth in claim 1, wherein said third axis is substantially coincident with said second axis.
 5. The actuator system set forth in claim 1, wherein said first link and said second link are coupled with a coupling comprising a connecting link having a first pivot and a second pivot.
 6. The actuator system set forth in claim 5, wherein said coupling comprises a bar link between said first pivot and said second pivot.
 7. The actuator system set forth in claim 1, wherein said first, link and said second link are coupled with a coupling comprising meshed gears.
 8. The actuator system set forth in claim 1, wherein said first link and said second link are coupled such that said first direction of rotation of said first link is opposite to said second direction of rotation of said second link.
 9. The actuator system set forth in claim 1, wherein said first link and said second link are coupled such that said first direction of rotation of said first link is the same as said second direction of rotation of said second link.
 10. The actuator system set forth in claim 1, and further comprising: a third actuator configured and arranged to power a third degree of freedom of said linkage system; a fourth actuator configured and arranged to power a fourth degree of freedom of said linkage system, said third degree of freedom and said fourth degree of freedom being independent degrees of freedom; said linkage system having a third link configured for rotary movement about a fourth axis relative to said reference structure; said linkage system having a fourth link configured for rotary movement about a fifth axis relative to said reference structure; said fourth axis and said fifth axis not being coincident with each other or with said first axis or said second axis; said third link and said fourth link coupled such that rotation of said third link about said fourth axis in a first direction causes rotation of said fourth link about said fifth axis in a second direction; wherein one of said third or fourth actuators is configured and arranged to drive rotation of said element about said first axis when said other of said third or fourth actuator is operatively locked.
 11. The actuator system set forth in claim 10, wherein one of said first, second, third or fourth actuators is configured and arranged to drive rotation of said element about said first axis when said others of said first, second, third and fourth actuators have failed open.
 12. The actuator system set forth in claim 10, wherein said third link and said fourth link are coupled such that said first direction of rotation of said third link is opposite to said second direction of rotation of said fourth link.
 13. The actuator system set forth in claim 10, wherein said third link and said fourth link are coupled such that said first direction of rotation of said third link is the same as said second direction of rotation of said fourth link.
 14. The actuator system as set forth in claim 1, wherein each of said actuators is supported by a bearing.
 15. The actuator system as set forth in claim 1, wherein said first actuator comprises a planetary gear stage.
 16. The actuator system as set forth in claim 1, wherein said linkage system comprises at least five links.
 17. The actuator system as set forth in claim 16, wherein said linkage system comprises a plurality of pivot joints between said links.
 18. The actuator system as set forth in claim 1, wherein said first actuator comprises a rotary actuator.
 19. The actuator system as set forth in claim 1, wherein said first actuator comprises a rotary motor, a hydraulic actuator, or an electric motor.
 20. The actuator system as set forth in claim 1, wherein said first link comprises a stator and said second link comprises a stator.
 21. The actuator system as set forth in claim 1, wherein each of said actuators comprises a brake.
 22. The actuator system as set forth in claim 1, and further comprising a brake configured and arranged to hold one of said degrees of freedom of said linkage system constant.
 23. The actuator system as set forth in claim 1, and further comprising a spring configured and arranged to bias one of said degrees of freedom of said linkage system.
 24. The actuator system as set forth in claim 23, wherein said spring is selected from a group consisting of a torsional spring, a linear spring, and a flexure.
 25. The actuator system as set forth in claim 1, and further comprising a damper configured and arranged to dampen rotation of at least one link in said linkage system.
 26. The actuator system as set forth in claim 25, wherein said damper is selected from a group consisting of a linear damper and a rotary damper.
 27. The actuator system as set forth in claim 1, wherein said first actuator and said second actuator comprise a stepper motor or a permanent magnet motor.
 28. The actuator system as set forth in claim 1, wherein said first actuator and said second actuator comprise a magnetic clutch.
 29. The actuator system as set forth in claim 1, wherein said element is selected from a group consisting of a shaft and an aircraft control surface.
 30. The actuator system as set forth in claim 1, wherein said element is selected from a group consisting of a wing spoiler, a flap, a flaperon and an aileron.
 31. The actuator system as set forth in claim 1, wherein said reference structure is selected from a group consisting of an actuator frame, an actuator housing and an airframe.
 32. An actuator system comprising: a controlled element configured for rotary movement about a first axis relative to a reference structure; a linkage system connected to said element and said reference structure; a first actuator configured and arranged to power a first degree of freedom of said linkage system; a hold device configured and arranged to selectively lock a second degree of freedom of said linkage system, said first degree of freedom and said second degree of freedom being independent degrees of freedom; said linkage system having a first link configured for rotary movement about a second axis relative to said reference structure; said first axis and said second axis not being coincident; said linkage system having a second link configured for rotary movement about a third axis relative to said reference structure; said first link and said second link coupled such that rotation of said first link about said second axis in a first direction causes rotation of said second link about said third axis in a second direction; said linkage system configured and arranged such that a first angle of rotation between said element and said reference structure may be driven independently of a second angle of rotation between said first link and said reference structure; wherein said hold device is configured and arranged to lock said second degree of freedom when said first actuator is operational and to unlock said second degree of freedom when said first actuator is operatively locked.
 33. The actuator system as set forth in claim 32, wherein said first axis and said second axis are substantially parallel and operatively offset a substantially constant distance.
 34. The actuator system as set forth in claim 33, wherein said first axis, said second axis and said third axis are substantially parallel and operatively offset a substantially constant distance.
 35. The actuator system as set forth in claim 32, wherein said third axis is substantially coincident with said second axis.
 36. The actuator system set forth in claim 32, wherein said first link and said second link are coupled such that said first direction of rotation of said first link is opposite to said second direction of rotation of said second link.
 37. The actuator system set forth in claim 32, wherein said first link and said second link are coupled such that said first direction of rotation of said first link is the same as said second direction of rotation of said second link.
 38. The actuator system set forth in claim 32, and further comprising: a second actuator configured and arranged to power a third degree of freedom of said linkage system; a second hold device configured and arranged to selectively lock a fourth degree of freedom of said linkage system, said third degree of freedom and said fourth degree of freedom being independent degrees of freedom; said linkage system having a third link configured for rotary movement about a fourth axis relative to said reference structure; said linkage system having a fourth link configured for rotary movement about a fifth axis relative to said reference structure; said fourth axis and said fifth axis not being coincident with each other or with said first axis or said second axis; said third link and said fourth link coupled such that rotation of said third link about said fourth axis in a first direction causes rotation of said fourth link about said fifth axis in a second direction; wherein said second hold device is configured and arranged to lock said fourth degree of freedom when said second actuator is operational and to unlock said fourth degree of freedom when said second actuator is operatively locked.
 39. The actuator system as set forth in claim 32, wherein said first actuator comprises a rotary actuator.
 40. The actuator system as set forth in claim 32, wherein said first link comprises a stator.
 41. The actuator system as set forth in claim 32, wherein said element is selected from a group consisting of a shaft and an aircraft control surface.
 42. The actuator system as set forth in claim 32, wherein said reference structure is selected from a group consisting of an actuator frame, an actuator housing and an airframe.
 43. An actuator system comprising: a controlled element configured for rotary movement about a first axis relative to a reference structure; a plurality of actuator units, each of said actuator units comprising: a linkage system connected to said element and said reference structure; a first actuator configured and arranged to power a first degree of freedom of said linkage system; a second actuator configured and arranged to power a second degree of freedom of said linkage system, said first degree of freedom and said second degree of freedom being independent degrees of freedom; said linkage system having a first link configured for rotary movement about a second axis relative to said reference structure; said first axis and said second axis not being coincident; said linkage system having a second link configured for rotary movement about a third axis relative to said reference structure; said first link and said second link coupled such that rotation of said first link about said second axis in a first direction causes rotation of said second link about said third axis in a second direction; said linkage system configured and arranged such that a first angle of rotation between said element and said reference structure may be driven independently of a second angle of rotation between said first link and said reference structure; wherein one of said first or second actuators is configured and arranged to drive rotation of said element about said first axis when said other of said first or second actuator is operatively locked.
 44. An actuator system comprising: a controlled element configured for rotary movement about a first axis relative to a reference structure; a plurality of actuator units, each of said actuator units comprising: a first actuator configured and arranged to power a first degree of freedom of said linkage system; a hold device configured and arranged to selectively lock a second degree of freedom of said linkage system, said first degree of freedom and said second degree of freedom being independent degrees of freedom; said linkage system having a first link configured for rotary movement about a second axis relative to said reference structure; said first axis and said second axis not being coincident; said linkage system having a second link configured for rotary movement about a third axis relative to said reference structure; said first link and said second link coupled such that rotation of said first link about said second axis in a first direction causes rotation of said second link about said third axis in a second direction; said linkage system configured and arranged such that a first angle of rotation between said element and said reference structure may be driven independently of a second angle of rotation between said first link and said reference structure; wherein said hold device is configured and arranged to lock said second degree of freedom when said first actuator is operational and to unlock said second degree of freedom when said first actuator is operatively locked.
 45. An actuator system comprising: a reference structure; an output member rotatably coupled to the reference structure for rotation about a first axis; a first actuator having a first member and a second member, the second member configured to rotate relative to the reference structure, the first member configured to rotate relative to the reference structure about a second axis, the first member configured to rotate relative to the reference structure independent of the rotation of the second member relative to the reference structure; a second actuator having a first member and a second member, the second member configured to rotate relative to the reference structure, the first member configured to rotate relative to the reference structure about a third axis, the first member configured to rotate relative to the reference structure independent of the rotation of the second member relative to the reference structure; a first link pivotally connected between the first member of the first actuator and the first member of the second actuator, the first member of the first actuator and the first member of the second actuator coupled such that rotation of the first member of the first actuator in a first direction causes rotation of the first member of the second actuator in a second direction; a second link pivotally connected between the second member of the first actuator and the output member.
 46. The actuator system of claim 1, and further comprising a third link pivotally connected between the second member of the second actuator and the output member.
 47. The actuator system of claim 1, wherein said first direction and said second direction are the same.
 48. The actuator system of claim 1, wherein said first direction and said second direction are opposite.
 49. The actuator system of claim 1, wherein said first axis and said third axis are coincident.
 50. The actuator system of claim 1, wherein the first member is a stator.
 51. The actuator system of claim 1, wherein the second member is a rotor.
 52. An actuator system, comprising: a reference structure; an output member rotatably coupled to the reference structure for rotation about a first axis; a first actuator having a first member and a second member, the second member configured to rotate relative to the reference structure, the first member configured to rotate relative to the reference structure about a second axis, the first member configured to rotate relative to the reference structure independent of the rotation of the second member relative to the reference structure; a holding device having a first member and a second member, the second member configured to rotate relative to the reference structure, the holding device configured to alternate between a first configuration where the rotational position of the first member relative to the second member is locked and a second position where the first and second members are free to rotate relative to each other; a first link pivotally connected between the first member of the first actuator and the first member of the holding device, the first member of the first actuator and the first member of the holding device coupled such that rotation of the first member of the first actuator in a first direction causes rotation of the first member of the holding device in a second direction; a second link pivotally connected between the second member of the first actuator and the output member; wherein the holding device moves from the first configuration to the second configuration when the first actuator is operatively locked.
 53. The actuator system of claim 52, and further comprising a third link pivotally connected between the second member of the holding device and the output member.
 54. The actuator system of claim 52, wherein the holding device is a magnetic clutch.
 55. The actuator system of claim 52, wherein said first direction and said second direction are the same.
 56. The actuator system of claim 52, wherein said first direction and said second direction are opposite.
 57. The actuator system of claim 52, wherein said first axis and said third axis are coincident.
 58. The actuator system of claim 52, wherein the first member is a stator.
 59. The actuator system of claim 52, wherein the second member is a rotor. 